New to me Maxim M250 - First outdoor boiler and need advice on areator removal

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New Member
Nov 30, 2022

We purchased a home in March of last year that had a Maxim M250 outdoor pellet stove installed in 2008. The previous owner said they always used it, and appears to be in OK shape. I did run the boiler for about 2 weeks based on the directions the previous owner gave me and it seemed to work well then the blower died and I left it off for the season. I have a new blower to put in but a few questions

I wanted to remove the burn chamber and clean out the inside and reading through the manual - It says I remove the aerator by turning it 1/4 turn counter-clockwise... it does not seem to want to move and is at a less-than-ideal angle to try to get my hands on it... any tips?

Anything else I should check or replace as preventative maintenance?

Any advice on how to best set the levels on the firestar controller for the blower rate at the 3 stages? when I first turned it on the last owner looked like they had it all maxed.... I turned them down some but not sure what I am doing.
In terms of feed/air rate, I would start with setting them the same. Meaning the air and feed matches. If you see unburnt pellets getting to the end of the burn chamber, then turn the air up 1 step. You don't want too much air than needed because it pushes the heat out of the chimney and is less efficient. In terms of where to set medium and high, you want high to be set as low as possible but still be able to handle your peak/maximum heat load. I have my maxim running 2 hvacs (100k and 90k btu heat exchangers) and hot water tank. I have high on its lowest setting (65%) and that is more than enough to handle my max load. Medium I change more often based on the weather. Mild weather I set it pretty low (20-30%). Then as it gets colder I'll eventually move up to 40-50%. You'll want to adjust medium to limit the amount of times you are shifting into high. The maxim is most efficient running in medium. Your hvac runtimes will really dictate your medium setting.
Thanks! I got the new blower installed and ran the boiler for about a week and all seemed to work well but it feels like it is burning a lot of pellets. If I had to guess I would say 2.5 - 3 bags per day for a 1500sq ft home. I did turn the settings down to around the lowest for low, medium and high and it seemed to hold temp ok when it was in the 30's outside without having to kick into high mode.

How many bags per day should I typically to expect to see in a normally insulated (not great but not bad) 90's era 1500 sq ft home?
2-3 bags per day sounds pretty high for you. My maxim is heating an 7000sq ft home. I've improved the insulation over the past couple years, but I would not classify it as well insulated. Has many windows, crappy doors. Although I've finally got it to the point where it seems well sealed, the thickness of the insulation in many areas is not great. That being said, right now I'm burning 1.6-1.8 bags per day with temperatures averaging around 45 degrees (24hr avg). When temperatures average down around 30 degrees, in the past that pushes me closer to 3 bags per day.

One thing I've learned about the maxim is efficiency of everything is key. You want to be able to run it as low as possible and/or have it go idle. What is your heat draw? Do you just have a single heat exchanger in a furnace? Are the boiler water pipes running to the house insulated? The next time you have a warmer day where your house heat doesn't need to run, pay attention to how long the maxim stays idle for. For example, if both my furnaces don't run meaning I have no load on my boiler, it takes 2-2.5hrs for it to drop 10 degrees, staying idle for that long. If I turn off the pump on boiler, so all water stays in boiler, I get 14hrs of idle time. I use thermopex insulated line and have insulated it anyplace it wasn't thermopex. The difference between the 14hrs and 2hrs just seems to be heat radiating passively from the heat exchangers, which is ok. If you want to dig into making it more efficient, you need to "collect data" to learn if you are losing heat anywhere.

Now keep in mind, I have the maxim 255pe. It's mostly the same , but over time the ignition process has continued to improve. The reason I mention this is because you mention "low" mode. On mine low is disabled by default and the boiler goes to idle instead (no feeding and absolutely no air). The igniter is an electric thermocouple in the 255pe. On previous versions of the maxim, the ignition process used propane. I "think" on the earlier maxims the ignition process wasn't as solid and they would use the low mode to keep a "coal bed" of pellets going over time to make reignition easier. So when I say to track your idle times, you may need to count low mode as idle as well.

Does your version of the maxim give you burn chamber temperature readings? The maxim can put out a ton of heat. With your size home it should be going idle/low for a majority of the day.
Thanks for the info! I just have one heat exchanger under the furnace for the home. That said I am thinking maybe I am getting heat loss in the piping to the house as I have a webcam pointed at the boiler and when there is no heat load it does seem to move between low and medium fairly frequently but I will re test and get true times soon. I can also see if I Can pull the

Is there an easy way to gauge the temp of output and return water with no heat load? Can I shoot a digital thermometer at the outside of the PEX or do I need to find a way to test the water temperature directly? The lines from the boiler run through what looks like drain tile with insulation wrapped around the pipe in the ground - they are red and blue for this run. once in the house crawl space it transitions to Orange pex and if I recall it does not have any insulation on for the 30 or so feet it runs to the furnace from the wall.... wonder if this could be my issue? Would I just use the foam pipe insulation to cover it?

The unit has propane ignition but it is not functioning... the previous home owner told me to get it going by using some charcoal lighter fluid on some pellets then turning the unit on after a min or so. I did try to connect a propane tank and there was no ignition from it. I guess when running in low it keeps the fire going? - would fixing this make an impact? the fire has never went out on me when running the unit after the initial startup.

I can pull the burn chamber heat from the controller as well - I will keep an eye on it in low and take some data.

Thanks for all the input!